One of the most serious problems facing the world today is the availability of clean fresh water for the well being and survival of mankind. Disposal into sewers and storm drains, or into the soil, of petroleum-based waste products, as well as waste water containing those and a variety of other contaminants, has become a major source of ground water contamination. Wells which supplied drinking water for thousands of people have become contaminated and unusable. This has given rise to numerous community, state and federal regulations setting standards for the protection of the environment, including standards for contaminant content of waste disposed of in local sewers, water courses and elsewhere.
In their zeal for environmental protection, some communities have set standards requiring the contaminant content of such waste waters to be so low that they could not be met by the use of presently available technology. As a result, some of these community standards have been reluctantly amended to permit higher levels of contaminant content which can be met with available technology.
There are many contaminants from numerous sources which are capable of polluting ground water and thereby threatening the environment, as well as the health of the populace. Some of such contaminants and sources thereof include lubricating oil, diesel fuel and grease from the auto and truck servicing industry; surfactant or soap laden waste water from laundry and dishwashing equipment; and ethylene glycol from the auto, truck and aircraft servicing industries, as well as from other industries where ethylene glycol is used in day to day operations.
Other sources of environmental pollution include agricultural run-off containing insecticides or other agricultural chemicals washed by rain or irrigation sprays from crops on which they were sprayed. Waste water from the photographic processing industry is a source of polluting metal salts, as is the electronic component manufacturing industry. An additional source of pollution is that resulting from backwashing of swimming pool filters in which the filtering medium is diatomaceous earth. Community standards in some areas of the country are presently so restrictive that the effluent from such back washing cannot be discharged into local sewers.
Because of the unavailability of any quick and efficient means for separating petroleum hydrocarbons, such as lubricating oil, grease and diesel fuel, as well as other contaminants from waste water containing the same, resort has been had by the automobile and truck service industry to the use of clarifiers. These commonly comprise a series of four open settling tanks, each of about 400 gallon capacity, disposed at different levels. Contaminated waste water is fed into the highest tank, and the overflow therefrom is fed into the second highest tank. With the exception of the lowest tank, the overflow from each tank is fed into the next lower tank in the series.
Much of the heavy oil, grease and solids in the waste water fed to the clarifier collect in the first and second tanks, and is periodically removed therefrom in the form of a sludge which is hauled away by licensed disposal services. For a period of time, the effluent from the lowermost tank is of a quality which meets local environmental standards. Eventually, however, the third tank in the series collects a significant amount of sludge and must be cleaned out along with the first two tanks, in order for the clarifier to continue to produce acceptable quality effluent.
Unfortunately a clarifier as just described produces additional environmental pollution, namely air pollution. More particularly, the waste water in the clarifier tanks tends, over time, to promote the generation of a foul smelling gas having an odor similar to that of sewer gas, which odor permeates the surrounding neighborhood.